[PATCH] lib: sbi: Ensure SBI extension is available

[Xiang W]

在 2023-04-27星期四的 09:00 +0200，Andrew Jones写道：
> On Thu, Apr 27, 2023 at 09:02:14AM +0800, Xiang W wrote:
> > 在 2023-04-26星期三的 19:27 +0200，Andrew Jones写道：
> > > Ensure attempts to invoke SBI extension functions fail with
> > > SBI_ERR_NOT_SUPPORTED when the extension's probe function has
> > > reported that the extension is not available. By adding a new
> > > status member to the extension which has three states
> > > (uninitialized, available, unavailable), we ensure that the
> > > probe function is only invoked once, lazily, upon first use.
> > 
> > Adding this state may cause errors. For example: the id numberof an extension is from extid_start to extid_end, which has an
> > unused ID. Searching for an ID in this extension will return NULL
> > if an unused ID is searched first.
> 
> Hi Xiang,
> 
> You're right. Either sbi_ecall_extension::status needs to be a function of
> extid, like probe is, or we should just always call probe (when it's
> available) and leave any optimizations to the individual probe functions.
> How about this?
> 
> diff --git a/lib/sbi/sbi_ecall.c b/lib/sbi/sbi_ecall.c
> index 76a1ae9ab733..c86e4e8c9134 100644
> --- a/lib/sbi/sbi_ecall.c
> +++ b/lib/sbi/sbi_ecall.c
> @@ -42,16 +42,18 @@ static SBI_LIST_HEAD(ecall_exts_list);
>  
>  struct sbi_ecall_extension *sbi_ecall_find_extension(unsigned long extid)
>  {
> -       struct sbi_ecall_extension *t, *ret = NULL;
> +       struct sbi_ecall_extension *t;
> +       unsigned long out_val;
>  
>         sbi_list_for_each_entry(t, &ecall_exts_list, head) {
>                 if (t->extid_start <= extid && extid <= t->extid_end) {
> -                       ret = t;
> -                       break;
> +                       if (t->probe && (t->probe(extid, &out_val) || !out_val))
> +                               return NULL;
> +                       return t;
>                 }
>         }
>  
> -       return ret;
> +       return NULL;
>  }
>  
>  int sbi_ecall_register_extension(struct sbi_ecall_extension *ext)
> 
> Thanks,
> drew
Good. If so modified we can modify sbi_ecall_base_probe as well.
As follows:

diff --git a/lib/sbi/sbi_ecall_base.c b/lib/sbi/sbi_ecall_base.c
index 786d2ac..e3aa02b 100644
--- a/lib/sbi/sbi_ecall_base.c
+++ b/lib/sbi/sbi_ecall_base.c
@@ -20,15 +20,7 @@ static int sbi_ecall_base_probe(unsigned long extid, unsigned long *out_val)
        struct sbi_ecall_extension *ext;
 
        ext = sbi_ecall_find_extension(extid);
-       if (!ext) {
-               *out_val = 0;
-               return 0;
-       }
-
-       if (ext->probe)
-               return ext->probe(extid, out_val);
-
-       *out_val = 1;
+       *out_val = ext ? 1 : 0;
        return 0;
 }

Regards,
Xiang W
> 
> > 
> > Regards,
> > Xiang W
> > > 
> > > Signed-off-by: Andrew Jones <ajones at ventanamicro.com>
> > > ---
> > >  include/sbi/sbi_ecall.h |  6 ++++++
> > >  lib/sbi/sbi_ecall.c     | 18 ++++++++++++++----
> > >  2 files changed, 20 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/include/sbi/sbi_ecall.h b/include/sbi/sbi_ecall.h
> > > index ff9bf8e2b435..8e31d0d91620 100644
> > > --- a/include/sbi/sbi_ecall.h
> > > +++ b/include/sbi/sbi_ecall.h
> > > @@ -20,10 +20,16 @@
> > >  struct sbi_trap_regs;
> > >  struct sbi_trap_info;
> > >  
> > > +enum sbi_ext_status {
> > > +       SBI_EXT_AVAILABLE = 1,
> > > +       SBI_EXT_UNAVAILABLE,
> > > +};
> > > +
> > >  struct sbi_ecall_extension {
> > >         struct sbi_dlist head;
> > >         unsigned long extid_start;
> > >         unsigned long extid_end;
> > > +       enum sbi_ext_status status;
> > >         int (* probe)(unsigned long extid, unsigned long *out_val);
> > >         int (* handle)(unsigned long extid, unsigned long funcid,
> > >                        const struct sbi_trap_regs *regs,
> > > diff --git a/lib/sbi/sbi_ecall.c b/lib/sbi/sbi_ecall.c
> > > index 76a1ae9ab733..20ff06f32dad 100644
> > > --- a/lib/sbi/sbi_ecall.c
> > > +++ b/lib/sbi/sbi_ecall.c
> > > @@ -42,16 +42,26 @@ static SBI_LIST_HEAD(ecall_exts_list);
> > >  
> > >  struct sbi_ecall_extension *sbi_ecall_find_extension(unsigned long extid)
> > >  {
> > > -       struct sbi_ecall_extension *t, *ret = NULL;
> > > +       struct sbi_ecall_extension *t;
> > > +       unsigned long out_val;
> > >  
> > >         sbi_list_for_each_entry(t, &ecall_exts_list, head) {
> > >                 if (t->extid_start <= extid && extid <= t->extid_end) {
> > > -                       ret = t;
> > > -                       break;
> > > +                       if (t->status == SBI_EXT_AVAILABLE)
> > > +                               return t;
> > > +                       if (t->status == SBI_EXT_UNAVAILABLE)
> > > +                               return NULL;
> > > +                       if (t->probe && (t->probe(extid, &out_val) || !out_val)) {
> > > +                               t->status = SBI_EXT_UNAVAILABLE;
> > > +                               return NULL;
> > > +                       }
> > > +
> > > +                       t->status = SBI_EXT_AVAILABLE;
> > > +                       return t;
> > >                 }
> > >         }
> > >  
> > > -       return ret;
> > > +       return NULL;
> > >  }
> > >  
> > >  int sbi_ecall_register_extension(struct sbi_ecall_extension *ext)
> > > -- 
> > > 2.39.2
> > > 
> > > 
> > 
> >